meter size barrier

The term meter size barrier (or one meter barrier) is used for aspects of planet formation that would seem to limit a planetary embryo's growth very roughly a meter in size (e.g., the range of centimeters to a few meters). A number of mechanisms fall within this definition, such as:

• bouncing barrier - while specks of dust might stick together when they meet, after a certain size, they seem more likely to bounce off each other.
• radial-drift barrier - the interaction of objects with a surrounding protoplanetary disk produces a tendency to migrate toward the star. The optimum size for such migration is on the order of a meter diameter, and at that size, all would seem to migrate into the star.
• fragmentation barrier - collisions between the embryos would be violent enough to break them apart.

The term meter size barrier is sometimes specifically intended to mean these last two.